Each year, the National Weather Service records the dates of the first fall season freeze and the last spring season freeze at hundreds of weather stations around the country. The Associated Press has collected data from 700 of the most complete locations between 1917 and 2017, and combined it with additional geographic information about the location of each station, calculated the mean and median for each location, and appended a NOAA-provided probability of first freeze dates, based between 1981 and 2010.
The raw data was provided by the National Centers for Environmental Information at the National Oceanic and Atmospheric Administration (NOAA). The data shows that the date of the first freeze of the year has fallen further down the calendar over the last several decades — and last year extended that trend. Last year, the average first frost day at the included stations was two weeks later than average, while the last frost of spring was nine days earlier.
Provided in collaboration with Associated PressProPublica & Associated Press